@article{10_4064_fm_46_3_243_275,
     author = {W. S{\l}owikowski},
     title = {A theory of extensions of map-systems {I}},
     journal = {Fundamenta Mathematicae},
     pages = {243--275},
     publisher = {mathdoc},
     volume = {46},
     number = {3},
     year = {1958},
     doi = {10.4064/fm-46-3-243-275},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/fm-46-3-243-275/}
}